This is a rectangle tsurikawa strap lock - designed to work with a 1 inch (25mm) nylon strap and 2x M4x10 screws (and 2x M4 nuts).

See the images of the assembled tsurikawa for an example of how the strap is assembled (with a snap button).

The strap, screws and nuts are available very cheap online - we suggest cutting the strap to a length of 35cm. A snap button can also be added to the tsurikawa strap (we suggest a 15mm snap button).